Uterus cells. Coloured transmission electron micrograph (TEM) of endometrial cells (yellow) from the uterus. These cells form the endometrium, the epithelial tissue lining inside the uterus. This is a vertical section through the cells, revealing the nuclei (pink) and the columnar shape of the cells. Across top is the top of the cells, forming the inner surface of the uterus, with a layer of brush-like cilia. Below the endometrium, there is a layer of connective tissue (red/green). The endometrium tissue increases in thickness until it detaches and is lost during a woman's menstrual period. It then regrows. Magnification: x2000 when printed 10cm wide.